This invention relates to flexible hose couplings, particularly couplings suitable for use with reinforced hose, a method of making such couplings, and die apparatus for making the couplings.
A variety of hose couplings for flexible rubber and plastic hoses are known including couplings suitable for textile reinforced and metal reinforced hose. In many cases these couplings comprise two main members, one of which is a nipple or end fitting having a portion thereof that is inserted into the end of the hose, and the other of which is a metal ferrule or sleeve member that extends about the exterior of the hose end. Often the ferrule is mechanically connected to the nipple member such as by means of threads or by an internal rim formed on one end of the ferrule, which end is driven into a circumferential groove formed in the nipple member. The ferrule or outer sleeve is made crimpable. By using a die set, the ferrule can be crimped or forced inwardly to clamp the hose end tightly between the ferrule and the nipple member.
U.S. Pat. No. 3,835,891 which issued Sep. 17, 1974 to Compoflex Company Limited is illustrative of a high pressure flexible hose developed in recent years and employing inner and outer helical wires for reinforcement. This hose may comprise several tubular layers of a plastics material which extends between the helical wires. These flexible layers can, for example, comprise fluorinated ethylene propylene copolymer. The inner helical wire is preferably coated with fluorinated ethylene propylene copolymer of Teflon.RTM.. For the conveyance of chemicals, layers of polypropylene fabric and polypropylene film are laid on the copolymer. The hose can be covered on its exterior with a coating of PVC (polyvinylchloride). By the use of helical wires on the inside and outside, this type of hose is capable not only of withstanding high internal pressures but it is also capable of full suction.
A metal coupling for the aforementioned wire reinforced hose is known in the industry, this coupling comprising a nipple member and a surrounding ferrule or sleeve. An external two start thread is formed on a section of the nipple having a reduced diameter. One of the grooves of this thread receives the inner helical wire of the hose while the other groove accommodates the inward bends of the flexible, tubular portion of the hose. The nipple is inserted into the end of the hose by a threading operation. An iron of steel ferrule is placed around the hose end and a flexible seal can be arranged adjacent the hose end between the nipple and the ferrule. The ferrule is provided with an inwardly extending flange or rim at one end. In addition to or instead of the aforementioned seal member, epoxy or other sealant material can be inserted between the ferrule and the end of the hose in order to provide a seal in the completed hose coupling. Once the sealing material is in place, the ferrule is then reduced in diameter by a suitable swaging process so that the end of the hose is compressed between the inside of the ferrule and the nipple. The swaging process results in a mechanical connection which helps to prevent the coupling from coming off the end of the hose. This connection is created between the inner helical wire and the threads or grooves formed on the exterior of the nipple.
Difficulties have been encountered in the art with the aforementioned coupling designed for a wire reinforced hose. One difficulty with this coupling and its method of manufacture arises from the tendency of the ferrule to bulge out during the manufacturing process. A bulging of the ferrule can result in seal failure. Another known difficulty is that the epoxy or secondary seal used in the coupling can sometimes be forced out of the space between the ferrule and the hose, leaving gaps or weaknesses in the seal.
U.S. Pat. No. 3,413,020 issued Nov. 26, 1968 to Samuel Moore & Company describes a fitting designed for composite tubing suitable for high pressure applications. The hose can be a polymeric composite tubing that has an inner helical wire extending about the interior of the tubing and laid along a helical cavity. For purposes of manufacturing the fitting, the last few turns of the helical wire are removed by means of pliers and wire cutters. The nipple or inner sleeve is formed with a helical, external thread which is threaded into the helical cavity formed in the hose end. The hose fitting is completed by an outer sleeve or ferrule having a series of internal teeth. These teeth engage against the outside of the hose end by crimping the outer sleeve inwardly. The ferrule is also held in place on the inner sleeve or nipple by means of threads formed at one end of the ferrule.
It is an object of the invention to provide a reinforced hose coupling which provides a secure connection between a hose end and the fitting itself and which is relatively inexpensive to manufacture. According to one aspect of the invention, the reinforced hose coupling is constructed for use with a reinforced hose end having an exterior helical wire. By projecting the end of the helical wire through holes formed in a depression in the side of the ferrule, not only a further mechanical connection between the hose end and the fitting is provided, but also an indicator that the hose coupling is in good condition for use.
It is a further object of the invention to provide a reinforced hose coupling wherein no separate sealant such as epoxy is required to seal the joint between the hose end and the fitting. The flexible tubular layers of the hose end extend beyond any helical wire that reinforces the hose and by clamping the extended tubular layers between the ferrule and the nipple member, a fluid tight seal can be formed.
It is an additional object of the invention to provide a method for making a coupling for reinforced flexible hose that has a helical wire extending about its interior. This manufacturing method can be carried out quickly using a first die and at least one follower die of smaller diameter on the metal ferrule of the coupling. It is the follower die or dies which cause the extension of the tubular layers to be clamped tightly between the ferrule and the nipple member.